Electric furnace.



A, E. GREENE. ELECTRIC FURNACE. APPLICATION FILED JAN. 23, 1911.

,1,O78,619 Patented Nov. 18, 19`3.

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ELECTRIC FURNACE.

Specification of Letters Patent Application led January 23, 1911. Serial No. 604,014.

To all whom t may concern Be it known that I, ALBERT E. GnnENn, citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Electric Furnaces, of which the following is a full, clear, concise, and exact description.

My invention relates to electric furnaces in which heat is generated by electric current induced in an electrical resistor.

My invention is applicable to heating furnaces for cold material or for fluids or for metals .to be melted or to be heated when charged into the furnace either in the cold or molten state, or both.

The object of my invention is to provide an efficient means of utilizing electric currents for heating by combining the heating effects of both primary and secondary transformer currents.

Myinvention contemplates more particularly in the combination with a suitable heating chamber for carrying the charge of a solid metal resistor forming the secondary of a transformer and a primary winding in inductive relation to said secondary, both said primary and lsaid secondary circuits' constituting resistors from which the heat generated by passage of electricalI current lherethrough may be transmittedk to the charge or material to be heated.

Other features of my invention relate to the details of construction whereby the secondary electric circuit constitutes also a magnetic circuit for the transformer; and

to means for controlling the induction of current in the charge in the furnace chamber.

The several .features of my invention may be more readily understood by reference to the accompanying drawings, 1n which- Figure lfied structure particularly adapted for heating material; Fig. 4 is a longitudinal, central section Aof a rotary type of furnace enibodying my invention; 5 is a View, partly in section, of a heating unit in which the secondary constitutes a magnetic circuit 'fitting joint with theupper part l5.

1 1s a central, vertical section of' one embodiment of my inventionparticularly adapted to melting metals; Fig. 2 is a p another embodiment ofv my invenwith respect to the primary and in certain cases constitutes the furnace chamber for carrying the charge; Fig. 6 is a sectional elevation of. a modification of my invention for preventing excessive induction in the charge itself; Fig. 7 is a plan section of the furnace shown in Fig. 6; Fig. 8 is a sectional elevation of a furnace embodying special features of my invention, and designed for controlling the amount of induction in the charge.

Referring to Fig. 1, 1 is the main chamber forming the junction of the smaller annular chambers 2, 2. The primary coils 3, 3 are embedded in the refractory lining 4, and the secondaries 7, 7 are preferably located in the bottom of the chambers 1 and 2 and covered with `a refractory lining 6 In Fig. ,2, the main chamber 8 isa round ot or Crucible. The primary 9, and the secondary 10, both constituting electrical resistor's, are embedded just vunderneath the refractory lining 11 and inside of the same.

A magnetic core 12 serves to increase the electrical eiiiciency of the furnace.

In Fig. 3 is shown a furnace suitable for heating any kind of material. The secondary may be made in two parts 15 and 16. The upper part 15 may have a shape corresponding to the bottom and sides of the.

chamber 13 in the walls of which it is embedded. The lower part 16 forms a close These two .parts '15, 16 also constitute a magnetic circuit, the direction of the magnetic flux being indicated by arrows. Thel primary 14 is preferably embedded in loose refractory material 18 inside the part 16; and the secondary circuit constituted by 15 and 16 bedded in refractory material 19. Where desired a layer of refractory material 20 may be applied over the inner surface of the Crucible formedy by the part 15. Where it is desired to melt brass, for` example, this refractory material may be of'ire clay.

A rotary furnace shown in Fig. 41. It consists of a main shell 21 and two ends 23 and 24. Inlet and outlet holes are shown at 25, 25 which may be closed by covers 26, 26 or left open for cont-inuous passa e of material through the furnace or use for any other suitable purpose, such as for passage of gas through the furnace. Secondary resistors 27 are located in the lining 22 and primary resistors 28 are located in close Patented Nov. 18,1913.V

is emproximity thereto. lnside the cylinder may be located another cylindrical heating part 32 hung o-n trunnions 29. The diameter of the cylinder 32 is considerably less than ythe internal diameter of the cylinder 21, thus leaving an annular space 3Q for the charge. The inner part 32 contains a core 3l preferably laminated. This core is inclosed in a casing 33 made in two or more sections insulated from each other by insulating material This casing 33 is preferably made of manganese steel to cut'down magnetic losses. lrimary coils 35 are embedded in the refractory 37 and secondary resistors 36 outsidel the primaries 35. The secondary circuit preferably consists as shown of a number of closed circuits in parallel.

lfig. 5 shows a heating unit which may be used in the hereinbefore described furnace or which may itselfserve, for instance, as the retaining vessel for heating fluids. This heating unit consists of a primary Winding 38, and a closed tubular secondary circuit 39, 39 preferably made in tvvo halves,I as shown, in order to facilitate repairs. The terminals of the primary 38 may be brought out through the opening 43. The path of the magnetic field produced by an alternating current in the primary is shown in general direction by the arrows. The two halves of thesecondary 39,39may be made of a metal more or less magnetic and thus serve to increase the magnetic 4lines of force derving through the coils of the primary 38. The

' primary 38 may be embedded in refractory material 4l or retained in any ,y other suitable Way. Space 42 is left between primary 38 and secondary 39 for receiving a uid charge to be heated. This may be charged through the opening 44, and poured out through the opening 43 or through any other suitable openings, or the heater may be used for the continuous passage of fluid therethrough.

Figs. G and 7 show a furnace 4heated only by heat generated in the secondary of a transformer. The heating'chamber 45 is partly surrounded by the resistor 46, 47. Said resistor forms the secondary of a transformer of Which 48 is the core and 49 the primary. The resistor is made of reduced cross-section in the part 46 Where the heat is desired, and large cro-ss-section Where heat is not desired.

Fi 8 shows an induction furnace provide with a secondary resistor 56 embedded beneaththe chamber 50 in refractory material. The primary coil 51 -is adjusted with respect to the secondary 56 by any suitable means such as screws 53, 53. The short, central core 52 is also movable by the screw 55. This arrangement provides means for limit-ingand cont-rolling the induction of current in the secondary 56 and in material in the chamber 50. The charge in the chamnoz/acre ber 50 also forms a complete secondary circuit around the core 52. 1 y

By the furnaces of the types ll have described above l can melt or heat such metals asi brass, copper, aluminum, zinc, lead, and the like from the cold irrespective of their form. To melt aluminum, for example, the cold aluminum metal is charged into the chamber of a furnace such as shown in Figs. l or 2. The current may then be put on the primary, and the furnace chamber heated by conduct-ion from both the prima-ry and secondary resistors until the aluminum melts. .Further heating may be regulated by the voltage applied to the primary. lt is, of course, preferable to keep the chamber full of reducing gas to prevent oxidation of aluminum. My invention aims primarily to provide suitable means for heating material in the form of small pieces or scrap, and subsequently when the pieces are fused together or melted, heating it by induced currents in the charge itself. By use of the furnace shown in Fig. 8 the induction may be controlled by varying the amount of magnetic fluir encircling the charge constituting a secondary circuit.

TW hen it is desired to heat material, for example to anneal steel castings, a furnace designed as shown in Figs. 2 or 3 may be used. Vf hen it is desired to heat liquids the secondary may be designed to hold these as shown in Fig. 3 or Fig. 5.

l am aware that it has been suggested to use acarbon Crucible or a platinum or other metal Crucible to heat a charge contained therein by currents induced from a primary through the aid of a magnetic core,'and I do not claim such an arrangement.

I do not limit my invention to the use of solid secondary resistors as, in certain cases these resistors may even melt and subsequently solidify again on the cooling of the furnace.

It is also understood that I do not limit myself to the use of metal for the secondary resistor but may use carbon or heated magnesite or any other suitable resistor.

l. In an electric furnace, the combination with a furnace chamber, of a transformer having a primary and a secondary coil both constituting resistors and arranged in proximity to said chamber, whereby heat generated in said primary and secondary coils is conducted to the charge. in the furnace chamber.

2. In an electric furnace, the combination with a furnace chamber, of electric resistors constituting the primary circuit for an alternating electric current flow, electrical resistors arranged in inductive relation to said primary circuit and therebyconstituting the secondary circuit, said'electrical resistors being arranged in proximity to said furnace mms3, ih@ combinatie' with a fummo@ chamba?, of@ prmay w d? ing having its mns embedded in the bG-am Wall of said chamber, and meac cms@ likewise' embedoed 'm the hmmm Wall said; furnace an@ having a cenm, vefcicaf 

